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Details on prehung entry door installation

In preparation for replacing several entry doors I've been reading some different step-by-step installation guides and I'd like to get some opinions on the best methods. I also watched the TOH video of Tom Silva on installing a prehung entry door.

I have not yet torn out the old doors and so I'm not sure what I'll find, but my house went through a major remodel in the mid-80s so I believe I'll find circa 1980 materials an methods (hoping for no surprises).

Most of the differences I have noticed between the TOH video, the manufacturer's instructions, and other DIY websites relate to the prep of the door cavity. Some sites say to use "z" flashing above the door, some say to use an adhesive membrane at the threshold, etc.

What do you experts recommend and just for reference I usually like to go above and beyond minimum code requirements. I like to have it done right once and hopefully I never have to do the same job twice....

Thanks for the insights!

Re: Details on prehung entry door installation

Definitely use a "Z channel", also known as a "drip cap"---if you don't you'll get water coming in the top of the new door as soon as it rains----I'm surprised that only one of the how-to videos covered this important step.

As noted in the videos, make sure you have enough height above the interior floor for the base of the new door frame & use the aluminum adhesive-backed tape to seal out the chance of any exterior water getting in.

There's a good chance the old work (old rough opening) isn't exactly plumb---this could be only on one side, or on all 4---check with a spirit level & check the rough opening measurements carefully before you buy the new door at the store; that way it should fit & you won't have to take it back---I would hang one new door at a time, rather than buy more than one door.

You should be able to hang the new frame reasonably plumb in the rough opening & use the shims, as noted in the videos to get the frame as plumb as possible---the trick is KEEPING all sides plumb as you start to install the screws holding the frame to the studs of the rough opening---I always drill a 1/8" pilot hole at various points thru the new frame near the shims (and any points that need it later) and use 3" colored deck screws (the same color as the new frame) to attach the frame to the rough opening studs---the deck screws have a waterproof coating & can be easily driven in using an electric drill with a phillips head fitting, or the special deck screw fitting that comes free inside the box of screws.

The advantage to this method is that you can adjust the driven deck screws in and out in small increments to get the frame plumb; mount the new door on the new frame using the hinge bolts & make your adjustments, as needed, on the deck screws using the forward & reverse levers on the drill until the door opens & closes without any binding; you can "fine tune" the adjustment on the deck screws by using a manual phillips head screwdriver for your adjustments.

The spray foam and pink insulation noted on the videos is absolutely essential for installing a new door that doesn't leak a lot of cold air into the home.

Re: Details on prehung entry door installation

Can the J channel of my vinyl siding serve as the drip cap? The J channel will sit directly on top and alongside of the brickmold of the casing.

Re: Details on prehung entry door installation

There has to be an overlapping edge that fits at least slightly over the top front of the brickmold (as a z channel/drip cap does), otherwise water will get in at the top front of the brickmold----you can always trim the lower "leg" of the z-channel if it will improve appearances, or see if they have a ready-made drip cap where they sell flashing in the big box stores.

I believe there is a method of installing the new exterior door without the brickmold, and framing the exterior top & sides with j-channel to prevent water entry---but you may not like the appearance without the brickmold----what do you have on there now with the old door???

Re: Details on prehung entry door installation

It depends on which door we're talking about, I have 5 that I'll be replacing. In some cases (where I have brick) the brickmold will nest inside of brick which will stand proud all around, in other cases (where I have vinyl siding) the vinyl J channel will stand proud of the brickmold all around. In other cases vinyl will stand proud around part of the door and there will be a part where the brickmold stands proud of foundation block.

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